Process for the dethydrogenation of hydrocarbons in the presence of sulfur dioxide and a calcium nickel phosphate catalyst



Feb. 7, 1961 R. F. STRINGER ETAL 2,971,

PROCESS FOR THE DEHYDROGENATION OF HYDROCARBONS IN THE PRESENCE OFSULFUR DIOXIDE AND A CALCIUM NICKEL PHOSPHATE CATALYST Filed Jan. 7,1958 24\ f /29 j 23 -H2S RECY CLE & H28

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I'll. l6 J-oLE|-'ms 11:5 AROMATICS 2o\ REACTOR\ 4' WATER 2 -+Q IQ A 22 uno HYDROCARBON 02 OR Q FEED- I AIR Attorney United States Patent PROCESSFOR THE DEHYDROGENATION OF HY- DROCARBONS IN THE PRESENCE OF SULFURDIOXIDE AND A CALCIUM NICKEL PHOS- PHATE CATALYST Richard FranklinStringer, Charles Newton Kimherlin, In, and Frances Sturgis McQuaid, allof Baton Rouge, La., assignors to Esso Research and Engineering Company,a corporation of Delaware Filed Jan. 7, 1958, Ser. No. 707,636

6 Claims. (Cl. 260-6735) This invention relates to the dehydrogenationof hydrocarbons and more particularly to the dehydrogenation ofhydrocarbons to produce aromatics and olefins.

Unsaturated hydrocarbons such as ethylene, propylene, buty enes, etc.,are important starting materials for the production of a variety ofchemical products, particularly polymers including low molecular weightpolymers useful as motor fuels as well as viscous plastic to solid highmolecular weight polymers.

It has been proposed to prepare such olefins, principally C to C olefinsand also diolefins such as butadiene and isoprene by passing saturatedhydrocarbons and mono-olefins such as butenes and amylenes through a bedof solid catalytic material maintained at suitable dehydrogenatingconditions. It has also been proposed to dehydrogenate naphthenes suchas cyclohexane and methyl cyclohexane to the corresponding aromatics. In

view of current demands for benzene and toluene as solvents, chemicalintermediates and premium motor fuel components, much effort is beingexpended to provide new and improved methods .for producing thesearomatics. A variety of catalysts and reaction conditions have beenproposed for these conversions in order to increase yields and improveselectivity for the production of certain desired specific products.

It has further been proposed, in this connection, to incorporate anoxidizing agent or hydrogen acceptor in .the hydrocarbon charge orreaction mixture in order to improve the conversion. For example Rosen,US. Patent No. 2,126,817, indicates that the conversion of butanes tobutenes is improved by including an oxide of sulfur, preferably S in thehydrocarbon feed to a catalytic dehydrogenation zone; It has also beensuggested that S0 N0 NO, 0 and CO act similarly to improvedehydrogenation. The mechanism by which these additives work is thesubject of considerable doubt or controversy. One school of thought isthat these materials react with the hydrogen produced by thedehydrogenation thereby causing a shift in the equilibrium of the.

reaction. Another school holds that the chief function of S0 in thissystem is to destructively oxidize hydrocarbons to produce very hightemperatures in the bed which induce conversion of other hydrocarbons.

It has been found, and in general it appears from the literature, thatin the conversion of saturated hydrocarbons to olefins and/or aromaticsby previously suggested processes, low conversions per pass are obtainedand production of undesirable low molecular weight hydrocarbons isexcessive. Low conversions with present day catalytic processes is due,in general, to thermodynamic equilibrium favoring the saturatedhydrocarbon. Poor selectivity is generally due to side reactions such aspyrolysis.

It is the object of this invention to provide the art with a new andimproved method for dehydrogenating hydrocarbons. It is also the objectof this invention to provide the art with an improved process fordehydrogenating hydrocarbons, particularly saturated hydrocarbons andmono olefins of six or more carbon atoms to olefins and/or aromatics.

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It is a further object of this invention to dehydrogenate saturatedhydrocarbons and mono-olefins of six or more carbon atoms to olefinsand/or aromatics with high conversions and good selectivity.

Other objects will appear more clearly from the detailed specificationand claims which follow.

It has now been found that hydrocarbons, including straight chainsaturated hydrocarbons and mono-olefins of six or more carbon atoms suchas N-hexane, cyclohexane, methyl cyclohexane, N-heptane and the like canbe very effectively dehydrogenated to form olefins and/or aromatics bytreatment thereof at elevated temperatures in the presence ofsulfurdioxide and a calcium nickel phosphate catalyst. The specificcombination of sulfur dioxide and this catalyst is extremely active andselective for dehydrogenating and aromatizing normal hexane. Forexampie, in a 7 hour run conversion of N-hexane to a liquid productcontaining 50 wt. percent benzene and 20 wt. percent hexenes can beobtained with this combination of sulfur dioxide and this catalyst at880 F. with essentially no light gas make.

The catalyst used in accordance with the present invention is formed byadding an aqueous solution of calcium and nickel salts containing from6.5 to 12 atoms of calcium per atom of nickel, to a solution of asoluble phosphate, preferably an ortho phosphate, in a neutral orpreferably alkaline condition. In a preferred embodiment the solution ofthe calcium and nickel salts is added with stirring to an aqueoussolution of dior triarnmonium phosphate in amount suificient to maintainthe mixture in alkaline conditon. Alternatively, the catalyst may beprepared by adding an aqueous solution of phosphoric acid and thecalcium and nickel salts to an aqueous solution of an alkali, preferablyammonia. The pH of the mixture should be between 7+ and 12, preferablyat about 7.7 to 8.3.

Examples of nickel and calcium salts which may be used as startingmaterials in preparing the catalyst are the chlorides, nitrates, andacetates, etc. of these metals. Examples of soluble phosphates that maybe employed as starting materials are disodium phosphate, trisodiumphosphate, dipotassium phosphate, diamzmonium phos phate, etc. Catalystproducts are particularly active when prepared by precipitation fromalkaline mixtures containing an ionizable basic nitrogen compound, e.g.ammonia, a water-soluble ammonium salt, or a watersoluble amine or aminesalt such as diethylamine, triethylamine or diethanolamine.

A normal calcium nickel phosphate is formed as fine flocks which settleslowly. After the fluocculent phosphate product has settled, it isseparated from the supernatant clear liquid and washed repeatedly withwater to remove soluble materials, particularly nickel salts andchloride ions, as completely as possible. The washed phosphate slurry isfiltered to remove a further amount of water, and the residue is driedat temperatures of 300 F. The dried product which is a hard gel may becrushed or otherwise reduced to granules or small lumps and used in thisform in a fixed bed reactor or may be reduced to a particle sizeconvenient for use in a fluidized bed reactor. Alternatively, the gelmay be pulverized, e.g. to a particle size capable of passing a 28 meshscreen and the product treated with a lubricant, preferabfy one capableof being removed by vaporization or oxidation such as graphite, avegetable oil, or a hydrocarbon oil, etc. and formed into pills orpellets.

If desired, the pulverized gel may be blended with catalyticallyinactive substances such as diatomaceous earth, normal calciumphosphate, low surface area or fused alumina or the like without losingits catalytic activity. In view of the fact that the catalyst mayeventually have carbonaceous deposits formed thereon which will have tobe burned off, it may be desirable to add an agent having the propertyof catalyzing the oxidation of carbon. For example, the incorporation ofone or two a regenerator vessel for burning of! carbonaceous depositswith suitable transfer lines for conveying catalyst from each vessel tothe other as is well known in the petroleum conversion art. In view ofthe exothermic nature of the percent chromic oxide in the catalystcomposition or pills reaction it is ordinarily desirable to includecooling coils facilitates the reactivation of the catalyst. or a steamboiler in the reaction Zone in order to control The hydrocarbons thatcan be efiectively dehydrotemperature. The feed rate to the reactor 1218 congenated in accordance with the present invention are trolled togive the desired conversion level. The reaction parafiins andmono-olefins containing 6 or more carbon products are withdrawn fromreactor 12 via line 13 and atoms per molecule preferably from 6 to 8carbon atoms passed to fractionator 14 where they are separated into permolecule. as well as mixtures of two or more of these an overhead streamcontaining hydrogen sulfide and other materials. The process isparticularly valuable in that it gases, removed through line 15,olefinic product Withis capable of converting n-hexane to benzene andhexencs drawn at 16, aromatics Withdrawn at 17 and Water and n-heptaneto toluene and heptenes. moved as bottoms. The hydrogen sulfide isremoved via The dehydrogenation is effected in a reaction chamber 5 lineand recycled through lines 19 and 20 to furnace 21 charged with theabove described catalyst. In view of the Where in admixture with oxygenor pp through fact that carbon and stainless steels appear to have a linthe hydrogen Sulfide is burned to Sulfur dioxide tendency to reducecatalyst activity it is preferred to use for recycle in the Proc ss. 7Vycor or Solaramic lined reactor vessels. The catalyst when is used asthe Source Of Oxygen it y be may be freed of lubricant or othervolatiles by heating to necessary to p the Overhead gases from line 15through 1000 F. in a stream of air, Dehydrogenation i ff d line 23 to asuitable scrubber 24 for the separation of the by passing th hydrocarbonf d Stock i h i h an hydrogen sulfide. A suitable absorbent such asdiethanol inert gas such as nitrogen steam, carbon dioxide or the amineis pp Via 25 to 1116 pp P of the like a d ith th hydrogen acceptor, lfdi id t scrubber so that countercurrent contact is effected withtemperatures of about 800 to 1000 F. preferably at about 25 the hydrogenSulfide-containing The gases freed of 850 to 950 F. The hydrocarbon feedrate is ordinarily 2 P oierhead from scrubber 24 through Outlet betweenabout 0.05 and about 0.5 v./v./hr., preferably 26 and the absorbentliquid is Withdrawn from scrubber about 0.1 v./v./hr. The amount ofsulfur dioxide added 24 Via 27 and passed to Stripper 28 Where the a ispreferably less than stoichiometric to the hydrocarbon is pp 05 PassingOverhead through 29 and thence feed in order to minimize the danger offorming elemental 30 to 20 for recycle t0 the furnace Z1 and reformationsulfur by the reaction of excess sulfur dioxide with the Into 2- The ppabsorbent is Withdrawn from th@ hydrogen sulfide formed. Reactionconditions, temperabottom of pp 23 and recycled Via line 25 t0 the tureand feed rate are so controlled as to effect at least scrubberconversion f the hydrocarbons per pass. 35 Thefollowing examplesdescribe certain Ways in which Reference is made to the accompanyingdrawing m the principle of this invention has been employed, but aretrating a diagrammatic flow plan for the process i not to be construedas limiting this invention. accordance with the present invention.EXAMPLE 1 r zs t0 h wing. Ihydrocarbon feed, for X- Normal hexane wasdehydrogenated by passing the 1 ah ppli d through ll and mixed 4 same atelevated temperatures over a calcium nickel phosy d ur s pp w t rough me1 Preferably phate catalyst which contains 56% P0 31% Ca, 5% Ni, Inf aomS J F lz l 1 and Passed at lefhperaiufes 1% Cr and 7% H O. In theseruns, 50 grams of this 0 8 0 to g 8 f The leaclol' 12 catalyst werearranged in a 1" x l5" Vycor reactor. 1 charged h a calcium hlclfelPhflsphale catalyst p The product from the reactor was collected in awet ice pared as described above. It is preferred to conduct the trapplus a Dry I trap d ana1yzed by gas chromatog. process in a fluidizedsolids system and it therefore will raphy. The process variables and theresults obtained be understood that 12 will comprise a reactor vesseland are summarized in Table I.

Table I DEHYDROGENA'IION WITH S01 PLUS A CATALYST cc. CALCIUM NICKELPHOSPHATE CA'I.. 1" x15" REACTOR Feed Product Analysis. wt. percent RunNo Cat Age V/V/Hr i???" Remarks Hr. I Moi Moi Mol flex one FE PercentPercent Percent n-Hexane Hexencs Benzene Na S09 Hcxanc O-O. 5 75 25 0.1825 95 Less than 5 No S01 in Feed.

0-1 20 20 0. 1 825 51 18 No elemental S in Recovery System. 0-0. 5 so 202o 0. 1 s25 66 7 27 Do. 0. 5-2 60 20 20 0. l 825 51 13 as Do. 2-2. 5 4836 16 0. 1 825 51 18 31 Elemental S formed in Recovery System. 2. 5-3. 560 20 20 0. 1 880 37 10 53 No elemental S formed in Recovery System. 3.5-3. 7 51 31 18 0.1 880 No Analysts Elemental S formed in RecoverySystem. 3. 7-5. 5 57 24 19 0.1 880 30 2O 50 No elemental S in RecoverySystem. 5. 5-6. 5 68 10 22 0.1 770 10 25 Elemental S formed in RecoverySystem. 6.5-7.5 S0 20 20 0.1 925 39 13 48 No elemental S in RecoverySystem. 7. 5-8.0 a7 24 19 0. 1 925 No Analysis Elemental S formed inRecovery System. (1-1 60 2O 20 0.1 880 No Analysis No Elemental S inRecovery System. 1 -2 e0 20 20 0. l 880 54 7 39 Do. 0-1 25 0.1 880 as a5 9 No soiin Feed. 1-2 60 20 20 0.1 880 67 3 30 N o elemental S inRecovery System. 7-8 60 20 20 0. 1 880 47 lo 43 Do. 8-9 75 25 0.1 880 so12 s No so, in Feed. 13-14 60 2o 20 0.1 880 28 9 63 No elemental S inRecovery System. 5-5. 5 0 31 e9 0. 5 880 77 s 15 o. 5. 5-6. 0 0 4e 54 o.5 aso e5 10 25 Do. 76. 5 0 46 54 0. 5 880 69 6 25 Elemental S inRecovery System.

l Catalyst pretreated with hydrocen for 30 minutes. Continuation of run13 but at hi her temperature. 3 Continuation of run 13 but at lowertemperature.

4 Continuation of run 13 but at hl'rhcr temperature. 5 Catalyst from run16 regenerated in air overnight. I Fresh calcium nickel phosphatecatalyst.

The following conclusions can be drawn from the foregoing data:

(l) Calcium nickel phosphate catalyst alone is inactive fordehydrogenation of normal hexane either initially or after it has beentreated with S0, and hydrocarbon feed (run 19). This catalyst iscommonly employed for butene dehydrogenation.

(2) Calcium nickel phosphate with sulfur dioxide is an extremely activecatalyst for dehydrogenation of normal hexane. At 880 F. conversion to20 mol percent hexenes plus 50 mol percent benzene was obtained (run14).

(3) Calcium nickel phosphate catalyst becomes more active with age onsulfur dioxide plus hydrocarbon feed. (Runs l1, 12, 13, 14, 15, 16 andrun 19.) The hydrogen pretreated catalyst (run 13) increased in activityfaster than the unreduced catalyst employed in run 19. These datasuggest that a sulfided form of the catalyst may contribute to activity.

(4) Without nitrogen diluent and at a higher hexane feed rate, theconversion or normal hexane decreases (run 24). However, the actualquantity of hexane converted per unit time is the same as that achievedat higher conversion with lower feed rates and nitrogen diluent.

(5) Air regeneration of calcium nickel phopshate catalyst does noteffect its activity (run 18).

(6) Increasing the reactor temperature from 825 F. to 880 F. gave anappreciable increase in conversion (run 14) but a further increase from880 F. to 925 F. did not increase conversion (run 16).

(7) If an excess of sulfur dioxide is used over that required forconverting hydrogen from dehydrogenation to H 5 and H 0, elementalsulfur appears in the product recovery system due to reaction of S withH 8.

In a similar series of experiments n-hexane was treated underessentially the same conditions in the presence of a potassiaandceria-promoted chromia-alumina catalyst and also in the presence of anickel on celite, 20 wt. percent nickel (reduced) on celite treated withH 8 for one hour before the run. The latter was very active but producedup to 8 percent of a material tentatively identified as alkylthiophenes. The promoted chromiaalumina catalyst gave relatively lowconversions (less than 35%) of aromatics plus olefins.

EXAMPLE 2 Normal hexane was reacted with sulfur dioxide by passing thesame at a feed rate of 0.1 v./v./hr. at 880 F. and atmospheric pressureover 250 cc. of a calicum nickel phosphate catalyst arranged in a 2" x15" Vycor reactor.

The process variables and the results obtained are summarized in TableH.

Table 11 Hour 2-3 -6 8-9 9-10 10.5-11.5

Feed:

Mol percent Nitrogen 54 50 O 0 0 M l percent SO: 22 27 53 59 46 M01percent Hexane 24 23 47 4t 54 Sulfur in Recovery System- N o No Yes YesYes Cat. Hours on Feed 3 6 9 10 11. 5 Liquid HG Recovery: Vol Percent onHexane Feed..- 63 64 63 50 70 Liquid Product O0mp.:

Wt. Percent n-l-lexanc--- 66 35 50 36 64 Wt. Percent Hexenes 4 16 10 V13 9 Wt. Percent Benzene -s 30 49 40 61 27 EXAMPLE 3 Normal hexane wasreacted with sulfur dioxide by passing the same at a feed rate of 0.1v./v./hr. at 975 F. over 50 cc. of a calcium nickel phosphate catalystcontaining 1.3 wt. percent of carbon arranged in a l" x 15" Vycorreactor. The process variables and results obtained are summarized inTable 111.

Table I" Hour 0-2 2-4 4-7 7-9 9-11 Feed:

Mol Percent Nitrogen 60 60 60 60 66 M01 Percent 20 12 Mo] Perc nt Hexane20 22 Sulfur in Recovery System.. No No No Yes Yes Get. Hours on Feed 24 7 9 11 Liquid HG Recovery: Vol. Percent on il'exnne Feed; 47 50 49 4470 Liquid Product (omp.:

Wt. Percent n-Hexane 37 37 29 29 47 Wt. Percent liexcnes 7 6 6 5 12 Wt.Percent Benzen 66 57 65 66 41 EXAMPLE 4 Normal heptane and cyclohexanewas reacted with sulfur dioxide by passing the same through a fluidizedbed of calcium nickel phosphate at a feed rate of 0.1 v./v./hr. atatmospheric pressure. The process variables and the results obtained aresummarized in Table IV.

Table V Feed n-Hcptane u-Hcptane cyclohexane Run. Fr 0-3 3-6 6-7 0-3 3-50-3 3-6 6-7 Reactor 'lemrx, F. 880 880 880 950 950 880 880 880 Feed, Me]percent: I

Mt 60 50 50 48 45 40 40 40 S0: 25 25 25 29 29 30 30 30 n-lleptanc 25 2525 23 23 Cycluhcxane---. 30 30 30 Liquid HG Recovery: Vol. Percent on HCFeed.. 66 70 83 52 60 72 72 75 Liquid Product Comp., Wt. Percent:

Heptane 78 70 66 41 32 Hcptenes Cycle-hexane- 47 40 29 Benzene 50 57 70Toluene 22 30' 34 45 56 Uuidentificd 14 l2 3 3 EXAMPLE 5 Normal hexanewas reacted with sulfur dioxide in contact with a fluidized bed ofcalcium nickel phosphate catalyst. The hexane feed rate was 0.1v./v./hr., temperature was 880 F. and pressure atmospheric. The processwas carried out in four six hour cycles on feed withcatalystregeneration with air at 880 F. between cycles. In each of thefour cycles that were run, the feed consisted of 60 mol percentnitrogen, 20 mol percent sulfur dioxide and 20 mol percent n-hexane. Theresults are summarized in Table V.

Sixteen wt. percent of catalyst were lost from the reactor during'cycle3 accounting for the lower yield obtained. 16 wt. percent of freshcatalyst (based on original charge) were added to the regeneratedcatalyst prior to the start of cycle 4.

The foregoing description contains a limited number of embodiments ofthe present invention. It will be understood that this invention is notlimited to the specific examples since numerous variations are possiblewithout departing from the scope of the following claims.

What is claimed is:

l. A method for the dehydrogenation of hydrocarbons containing at leastsix carbon atoms per molecule to form aromatics and olefins whichcomprises reacting said hydrocarbons with sulfur dioxide atelevatedtemper- .atures in contact with a calcium nickel phosphate catalyst. 2.The process for dehydrogenating hydrocarbons containing at least sixcarbon atoms per molecule to olefins and aromatics which comprisesreacting the said hydrocarbons with sulfur dioxide at temperatures offrom 800 to l000 FLin contact with a calcium nickel phosphate catalystuntil at least 40% of the hydrocarbons is converted to olefins andaromatics.

.3. The process as defined in claim 2 in which the amount of sulfurdioxide is less than stoichiometric with respect to the hydrocarbonfeed;

4. Theyrocess as defined in claim 3 in which the catcium nickelphosphate catalyst consists of'56% P0 31% Ca, 5% Ni. 1% Cr and 7% H O. a

-5. The process as defined in claim 4 in which the hydrocarbon feed rateis between 0.05 and 0.5 v./v./hf.

6. The process as defined in claim '5 inwhich thezhydrocarbon feed ,rateis about 0.1 v./v./hr. and themeaction temperature is 850-950 F.

References Cited in the fileof this patent UNITED STATES PATENTS2,126,817 Rosen Aug. 16,1938 2,324,073 Gaylor et a1. July 13,19432,394,750 Cole et a]. Feb. 12, 1946 2,754,345 Kirshenbaum July 10, 19562,831,042 Sieg Apr. 15, 1958 2,856,441 Murray Oct. 14, 1958 2,867,677Murray Jan. 6, 1959 2,884,473 Reilly et a1. ....,Apr. 28, 1 959

1. A METHOD FOR THE DEHYDROGENATION OF HYDROCARBONS CONTAINING AT LEASTSIX CARBON ATOMS PER MOLECULE TO FORM AROMATICS AND OLEFINS WHICHCOMPRISES REACTING SAID HYDROCARBONS WITH SULFUR DIOXIDE AT ELEVATEDTEMPERATURES IN CONTACT WITH A CALCIUM NICKEL PHOSPHATE CATALYST.